A Passive Lossless Snubber for Bidirectional Buck/Boost Converter

A passive lossless snubber for soft-switching Bidirectional Buck/boost Converter (BBC) is proposed in this paper. Although the conventional lossless snubbers can effectively alleviate the switching losses during turn on and turn off transients, they can be applied to only the unidirectional converters, but not a bidirectional converter. On the other hand, the proposed lossless snubber is able to improve the switching losses of the bidirectional Pulse Width Modulated (PWM) converters. Moreover, since the synchronous rectifier (SR) switch is softly turned off with the aid of snubber inductor, its reverse recovery characteristics can be considerably improved. The operational principle, theoretical analysis, and design considerations are presented. To confirm the operation, validity, and features of the proposed circuit, experimental results from a 3kW, 220-350 V-dc prototype are presented.